Making Deep Space and Nuclear Rockets Safe for Astronauts: PART II 
by

Bruce Behrhorst

[  PART I   ]

The question of life's existence beyond Earth remains unanswered in the technical legal sense. To most, the question is a small consolation for which we already know the answer to.

Two recent space missions have given us a small glimpse at what might be in-store for the existence of extraterrestrial life forms even at the cellular level. Spacecraft observations of the landing area of one of NASA's two Mars Rovers, "Opportunity" indicate there was an enormous sea or lake covering the region in the past. Maybe a surface area body of water comparable to all of the Great Lakes combined. As most space enthusiasts know, water is the necessary ingredient to life as we know it. We understand organisms on Earth seem to pop-up in the most inhospitable of places able to thrive and sustain themselves indefinitely.

Another recent space mission Cassini/Huygens gives us a stark reminder that icy Moons do indeed exist and some equipped with vast oceans.

A bigger question remains to be reconciled if we take the liberty to say, "Extraterrestrial life forms do exist in our Solar System down to the cellular level." Could by some extension a human being adapt to live and thrive on habitats apart from Earth indefinitely? First a transportation system/s must be established. Systems that can guarantee the safe delivery and return of humans in the shortest transit times possible under the least stressful regime possible. Of course human habitat survival also depends upon the ability to protect humans and habitat that in some cases will mean semi permanent or permanent residence in harsh environments. Nascent humans' arrival to these worlds will depend on the ability to mine and process potable water for various basic uses and the construction of habitable structures. In order for the most rudimentary survival prerequisites to be successful radiation mitigation (shielding) strategies for deep space, onboard and extraterrestrial environments sources of radiation (Mars double the radiation of Earth) must be developed and implemented to give a high degree of success in these long duration missions. This could lead to the next phase in human biomolecular change - the ability to show signs of physical adaptations to different heavenly bodies within our Solar System.

Out of 3.2 billion base pairs the present human genome make-up is composed of 30,000 - 40,000 genes, "Almost every cell in the human body contains the same set of genes. But not all of the genes are used, or expressed, by those cells. For example, some processes that are particular to cells in the liver are completely unused in brain cells. Ever since genomic research began, scientists have been searching the tangle of DNA for the expressed genes, the ones that really matter.

If one thinks of the nucleus of a cell as a library, then the chromosomes in the cell are bookshelves and the genes are the books on each shelf. Almost every cell in an organism contains the same libraries and the same sets of books. The books represent all of the information (the DNA) that every cell in the body needs so that it can grow and carry out its various functions. Two challenges complicate the process of locating our genes: Not all of the genes are expressed in any one tissue, and less than 10% of our DNA is actually used to make genes. Only occasional passages in the library’s written material are important."¹

Much of the DNA is unused called "Introns" , "Exons" (useful parts, expressed genes) are interrupted by Introns, Exons account for only about 1% of all DNA, 99% is unused (unexpressed) Introns when mRNA is made, Exons put together after clipping Introns out Exons can be put together in different arrangements to make different proteins some genes show up in multiple copies on different chromosomes some pieces of DNA can move around on a chromosome. Other life forms also possess this overabundant unused DNA, except that some of their "Redundant" DNA has gradually changed and mutated into other usable genetic material, But despite this mutation, their functional genes have never altered. This is all a product of billions of years of life on planet Earth.

" Scientists are still grappling with this vexatious conundrum, and are gradually coming to believe that any genetic “blueprints” of other forms - such those of laboratory mice, for example, which correspond in certain areas with our own - when our helixes are compared with theirs, show that those same sections of our human genetic code must perform some worthwhile, vital function. The only remaining problem now, is what - and how do we find out?" ² Researchers have been able to manipulate genetic code in mice, but in humans this raises ethical questions that need to be clearly resolved before work in this area is to progress in earnest. Whether by natural or direct genetic manipulation processes, can Homo Sapiens adapt to extraterrestrial worlds successfully? I believe we can given the proper tools and the will to do so.

The ' will ' to let science separate between fact and fiction is still evident today as it was in the past and will continue being a source of criticism. It's a legacy of free societies and as a free society those that take the time to inform themselves tend to support accurately the means and method which advance its society. In today's media, confusion and misinformation about space radiation is a source of controversy. A New York Times article printed 12/9/2003 by Mathew Wald, "Mars Mission's Invisible Enemy: Radiation" touting the extreme danger of space radiation drew plenty of criticism by the Mars Society calling on the NY Times to print a correction. The New York Times as with other media is no stranger to inaccurate reporting - at one time even calling the father of American Rocketry Dr. Robert Goddard's work an impossibility. The only hope is that emotional reporting by established media be replaced with investments in accurate reporting.

SHIELDING AGAINST A HARMFUL SPACE RADIATION ENVIRONMENT

The purpose and vision of NASA’s Space Radiation Health Project (SRHP) is to achieve human exploration and development of space without exceeding an acceptable level of risk from exposure to space radiation.

  An important safety concern for long term space travel is the health effects from space radiation. Possible health risks include cancer, cataracts, acute radiation sickness, hereditary effects, and damage to the central nervous system. NASA has been developing ground based research facilities to simulate the space radiation environment and to analyze biological effects at the molecular and cellular level. These facilities will also be used to understand and mitigate the biological effects of space radiation on astronauts, to ensure proper calibration of the doses received by astronauts on the International Space Station, and to develop advanced material concepts for improved radiation shielding for future exploration missions to Mars.
For over 35 years, NASA has been collecting and monitoring the radiation doses received by all NASA astronauts that traveled into space during the Gemini, Apollo, Skylab, Space Shuttle, Mir, and the International Space Station programs. The data on the amount of space radiation and its composition is now more available and well understood. [website statement]

FEATURE INTERVIEW

This summer 2004 I had a chance to speak with Dr. Francis Cucinotta to give NS readers a brief sense of what's involved in the complex world of devising strategies that protect astronauts from the effects of space radiation in particular radiation protection studies of the International Space Station and Extravehicular Activity (EVA) Space Suits. See study [nasa/tp-2003-212051].

BB: Today I'm speaking with Dr. Francis Cucinotta, at the NASA Nuclear Safety Office at the Johnson Space Center.

FC: Correction...The Radiation Health Office and I'm the Radiation Health Officer for the Astronauts.

BB: What is the Radiation Health Office at JSC and what are the duties of a Radiation Health Officer?

FC: Ok...We advise the Astronauts on the risks. We calculate their risk from dosimetry and computer models to determine cancer risks we also do cataract risk at this time. We also have the operational programs during missions we track the conditions of space weather which means the Sun, Solar Particle Events (SPE's) or disturbances of the Earth's magnetic field. How they might impact crew on the Space Station or the Space Shuttle especially if they're doing space walks.

BB: Historically could you point to instances were astronauts were required to use nuclear material in order to perform major missions in space?

FC: Nuclear material?

BB: Yes.

FC: Well...Yes, there was an experiment on Apollo where they used an RTG (Radioisotope Thermal Generator containing Plutonium).

BB: How would you characterize the astronaut corps toward space nuclear power and propulsion, are they in favor of using this technology in the future?

FC: I think overall they are. If it would substantially shorten long missions. One proposal that I know of called, "VASMIR Project" where they have a goal of a complete Mars Mission in less than a year using nuclear propulsion. People are very much in favor of that idea. But, if they use nuclear propulsion and not shorten mission transit times then they would be against it.

BB: Have any past or present astronauts fell ill as a result of prolonged exposure to space radiation or onboard sources of radiation?

FC: Not that we know of.

BB: In your estimation what are the more acute dangers in prolonged astronaut activity in space due to deep space background radiation and onboard sources of radiation?

FC: There's always the risk of large SPE's. In the scientific literature or news media stories it's been over estimated for inside space vehicle radiation, if you actually look at the amount of shielding and the shielding on the body correctly there's really no acute risk, but for space walks especially for Moon missions on the surface of the Moon where you would be outside a lot there would be a possibility of a large SPE event producing acute effects.

BB: Like energetic electrons or HZE particles?

FC: When I say, 'solar particles' it's mostly protons. So you will always have this risk the Sun will have during a mission spewing out a Coronal Mass Ejection (CME) which leads to a high dose of Protons. This can be reasonably well shielded if you're inside a space vehicle and especially if you're prepared for such events when outside a space vehicle or habitat. If you didn't know the event has started you would have the possibility of acute effects occurring.

BB: Could you give us an update on the 34 million dollar NASA space radiation lab at Brookhaven National Laboratory (BNL) which conducts experiments to simulate and study cosmic ray bombardment shielding on materials and biological systems to enable explorers to safely traverse our solar system and the recent announcement of additional grants totaling $13.5 million for space radiation materials research?

FC: Ok...The facility was opened July 2003. We use the term 'campaigns' when NASA funded investigators use the facility for a four to six week period. Right now, it's three 'campaigns' a year or so looking at 15-to-18 weeks a year where our investigators are there. So we already had four of these 'campaigns'. The next one will start the last week in August we call it 'NSRL 5'. Already in just over a year we have equaled the rate of research that we had over the previous four years. So what's happening by having this facility, where we can use the ion beams as much as possible we're quadrupling the rate we're learning about the effects of space radiation on cells and tissue.

BB: I imagine Nasa is trying to label priority in the following areas:

• Molecular radiation biology of carcinogenesis; meaning improved estimates of cancer risks from space radiation using genetic and molecular-based animal or tissue models, historical nuclear mishaps incidents studies on cancer risk predictability.
  
• CNS radiobiology understanding need to estimate risk to CNS (central nervous system) to short term/long term low doses effects of HZE (High Energy high charge Z ions) heavy ion particles and proton doses.
  
• Models of non-cancer or degenerative tissue risks: estimation of proton and HZE ions BRYNTRN (Brayon transport code model) and HZETRN (NASA Space Radiation Transport Code).
  
• Individual susceptibility; understanding genetic or epi-genetic factors that contribute to sensitivity or resistance to radiation and development to molecular markers of cancer, CNS or cataract risks.
  
• Cell and Molecular biology
  
• Multi-functional shielding materials
  
• Discovery of biological countermeasures
  

FC: Yes, and this is quite a lot of activity. I think a simple way to explain it for people that are familiar somewhat with radiation effects; have heard of the concept 'Radiation dose'. The problem with that quantity, is that what it really means precisely is the amount of energy deposited in bulk matter, bulk material, so when you start looking at some structured biomolecule like DNA or the proteins that interact with DNA inside a cell it loses its usefulness as a descriptor of radiation effects. There's a lot of structure in biology and just average energy in bulk matter really has no descriptive power. So, how do you estimate risk? Usually what's done is to look at humans that have been exposed to radiation and then rank them by their dose that fit an equation that describes the risk as a function of dose in that population. So the big problem is, there's no data like that for the kinds of radiation types that we're particularly interested in for the space missions of the future. You have to go back to energy depositions in biomolecules like DNA you'll find it's akin to comparing apples to oranges. When you compare the radiation on the ground like Gamma rays, X-rays to Heavy ions in space and the type of damage to molecules is very distinct. So in conclusion, the way we estimate risk is the big problem, we could be high, we could be low. Until we understand how well we can estimate the risk it's a problem for long duration space missions.

BB: I noticed one component on the 'NASA list of priorities' the discovery of biological countermeasures like diet, preventative medical therapy, skin creams, radiation vaccines and in-flight fat or glandular frozen stem cell replacement therapy etc. What about these countermeasures?

FC: The countermeasures is the next phase of our program after we can reliably project the risks. What we can do then is reliably design or validate a biological countermeasure. It's the same issue. How do you know if a countermeasure is going to work for Iron particles? You might look at a countermeasure that's been used for Gamma ray protection, but since the damage to biomolecules in cells is so much different you wouldn't understand if its going to work or what the efficiency of that countermeasure is. With the exception of acute risks as we know, for things like nausea or vomiting caused by radiation we need to know, it's a very simple measure of losing cells and we can predict how well different types of radiation will kill cells (tissue cell loss).

Some of the countermeasures that have been developed are... ok.

A countermeasure for decreasing the risk of cancer or damage to the brain we have really poor ability to understand if or how well the countermeasure is going to work.
So this first phase of the program is to understand the mechanisms of how the damage occurs and the second phase will be more about the countermeasures you brought up.

BB:To date have any 'flown' astronauts been advised by flight surgeons and the Nasa space radiation health project to 'ground' personnel due to surpassing allowable exposures?
Are missions rated due to the cost against astronaut's allowable career exposure on a per mission or overall life span to the individual? In other words are recommended regulatory dose limits set for random (Stochastic) and deterministic (non-stochastic) for career dose exposure and do these regulatory dose limits change as new material shielding data studies change recommended dose limits?
(radiation dose limits for space activities allow exposures that are higher than regulatory limits for terrestrial workers in the United States. Only EVA's that occur during extreme condition have the potential to exceed the thresholds for these effects.)

FC: We have two types of limits. We have limits for acute and deterministic effects these are 30 days and one year limits to Blood Forming Organs (BFO's) is the major one. We also have career limits, so the astronauts have to adhere to both of those limits. To date no one has been 'grounded' for their space exposures relative to those limits. The NASA career dose limits correspond to the estimate of 3% that would cause fatal cancer (3% excess lifetime risk of fatal cancer for a 10 year active career).

BB: This 3% factor... Is this written in stone?

FC: Yes, these are rules that NASA follows that are regulated by the Department of Labor (OSHA). We know below a certain age those persons would not be able to perform long missions because the dose limits are age-dependent. For example; a 25 year old person would not be able to spend a year in space would be an example, because the younger you are the higher the cancer risk from radiation. So far the typical age for astronauts which is 15 years older (40 yrs.) there hasn't been any problems.

BB: Which space suit is best apt to protect against space radiation in the region of Low Earth Orbit, NASA's EMU (extravehicular mobility unit) or the Russian Space Agencies' Orlan-M suit ?

FC: We did some measurements with both space suits at Loma Linda University with protons and electrons. There were really no conclusions that one was better than the other.

BB: So the space suits performed about the same?

FC: There were areas on one that were a little better than the other, but the variability was such that you couldn't conclude one way or the other.

BB: I was led to understand by Dr. John Wilson some of the metal alloys used to make up swivel joints that permit articulation of limbs on the EMU suit could be replaced with a lighter composite type material, this to prevent the effect of deposit on metals due to secondary radiation 'holding quality' that could increase CA skin risk. What sort of modification recommendations to the current EMU suit would be passed on to the principle contractor Hamilton Sundstrand to comply?

FC: We look at all the different organs at risk, for example: the skin, eye and the internal organs like the lungs, stomach it turns out the body itself provides most of the protection for the lungs or the stomach, the really deep seated tissues. For the less shielded tissues like skin these kind of things that Dr. John Wilson mentions become more important. Improvements to the joints and cloth material construction become more important in protecting the skin especially from lower energy radiation from a solar particles event.

BB: Is there like a 'polyethylene tarp' or storm shield that is placed according to directionality of penetrating trapped protons impinging from incoming CME's and SPE's energetic fast flux particles and the individual performing EVA on ISS at for example 51.6 degree (high) inclination orbits during a light SPE storm?

FC: What we have is a sleep station also called, 'crew quarters' in the U.S. Lab module and we had the opportunity to add polyethylene shielding to three of the walls of that sleep station to better protect it and we chose the walls based on directionality against trapped radiation, but also cosmic rays so we picked directions where trapped radiation would come in and also directions away from facing the Earth because Cosmic radiation do not penetrate through the Earth.

BB: If you were an Astronaut orbiting at a 51.6 degree inclination during a light SPE storm. An anomaly situation arose causing you to be caught outside the spacecraft. Isn't there like a polyethylene tent an astronaut could slip into for shelter?

FC: Well...They could just go against the spacecraft because you would have what is called, "Two Pi" shielding there that would be the best approach. The astronaut would pick a part of the spacecraft where relative position to the Earth were the solar protons would not come through the Earth. The Earth provides a shield and so does the spacecraft it could protect you in a different direction. You also have the Earth’s magnetic field so that an SPE would only impact an EVA at northern or southern latitudes.

BB: Do you advise mission planners to avoid 'hot spots' like off the southeastern coast of South America?

FC: The EVA's are always planned so that you would miss the weak magnetic part of the orbits. So everyday even for the really large historical SPE's there's about a 10-to-12 hour window were an EVA even during an SPE would be safe. They always plan to be in that window. That means times of the day were you're not hitting those southern or northern magnetic latitudes and your not going through the south atlantic anomaly layer where you have the highest trapped proton exposure. We work it out out with radiation environmental models where the window of opportunity to do safe EVA's occurs - and that's what NASA does.

BB:In regards to the difficult task of optimizing radiation shielding on tests of EMU/ORLAN-M using energetic protons. Could you explain the results suggesting a naïve assumption that adding mass can reduce risk is not supported by data which show that reducing the dose delivered at or near the skin by low-energy particles may increase the dose delivered by energetic particles (fluxes of high-LET secondary particles) to points deeper in the body?

FC: Back up...You said, "...TESS and EMU." In the same sentence. They're two different things, the 'TESS' is the sleep station or crew quarter inside the ISS Lab module and the EMU is the spacesuit used for space walks. The 'TESS' has the polyethylene the EMU does not. I'm confused by your question.

BB: Oh... I see. So one is for the suit and the other is for the cabin?

FC: So far there's no polyethylene [protection] that's been used for an EMU. Conceptually people are looking at models of EMU's or spacesuit which have polyethylene components, but none of that has been implemented at this point.

BB: It hasn't yet !

FC: No...

BB: If this was implemented would this garment or layer of whatever it is go next to the skin by the water flow [coolant tubes] layer?

FC: For example; if Nasa returns to the Moon we now have a chance to design a new spacesuit. One concept is to have a cloth of polyethylene. The material of the spacesuit is actually made out of that and it would provide extra protection throughout most of the skin.
Then you would also look at the helmet and the backpack as other areas where you might improve material selection.

BB: Essentially what your saying, is out of the approx. 260lbs of weight [suite] there wouldn't be much of a difference that you would add [weight] in modifying the suit.

FC: In a redesign you would pick different materials and try to optimize it that way. Other things you could do to that might impact mass a little, is to look at the coolant tubes to try and structure those to provide more protection. That would have to be considered along with the typical other criteria like thermal...Things like that.

BB: Essentially the manipulation of the redesigned suit will only cover a certain radiation that you're hoping to mitigate; meaning it will not shield everything 100%?

FC: That’s correct. A redesigned suit improve the protection from solar particle events, but very little for galactic cosmic rays which have very high penetration power in all materials.

BB: Could you comment on Blood Forming Organs BFO cells with regards to proton low energy exposure. Apparently these cells remain sensitive to splash electrons no matter what thickness shielding material is placed to remedy cell dose absorption which causes transmissible chromosomal/genomic instability in hematopoietic stem cells of mice. In this regard how much of this is attributed to weightlessness and/or radiation? What I'm trying to say with this question is, which is more of a problem the effects of radiation on BFO's or osteoporosis bone mass loss?

FC: I don't think the effects of radiation on bone loss isn't understood at all. I don't know if you can say it does that at all. Radiation effects on bone marrow system would be important to SPE's. You mentioned 'splash electrons' that's a really small dose; there's really no impact to astronauts. It's very penetrating so there's not much you can do with shielding, but it's also a small dose from 'splash electrons' it's not really a consideration. When you're on the Moon or Mars you don't have that problem.

BB: What were the type of cells used in most cases with radiation studies, animal or human?

FC: They were just mouse cells. There was only one study. Most of those studies were physics measurements not a biology experiment.

BB:Could one immerse the phantom (radiation test dummy) in an EMU filled with plain water and measure absorbed dose, would there be a difference?

FC: Immerse a phantom in a water tank?

BB: Just filling the spacesuit up with water with the phantom in it.

FC: Yes...There should be some difference. Depends on what kind of radiation... Things like that.

BB: Female EVA limit specifications for female exposures, which are approx. 40% less than those for males, radiosensitive organs unique in females require additional attention. Is there a significant difference between the sexes ?

FC: In what..? The dose limits?

BB: Yeah.

FC: The dose limits are based on equality of risk they are both being limited to the 3% increase of fatal cancer risk. So when you estimate the dose that causes that it depends on gender and age. The age part is due to the latency mainly. It's a complex distribution of time-to-exposure. The probability of time from exposure to the occurrence of a cancer if in fact it happened at all.

Leukemia will come earliest usually within the first 20 years. Lung cancers would occur much longer 20-40 years after exposure. The older you are dictates you might die of something else before radiation would cause a cancer.

Another cause for an age dependence of cancer risk is related to the changing number of epithelial cells with age. For example, in breast cancer after menopause the number of target cells that are available that cause cancer on the breast declines rapidly so you're much less risk at older age than younger ages with regards to radiation and breast cancer risk.

The other differences are gender differences. The breast and ovaries are fairly sensitive to radiation that increases the risk for females relative to male. From human epidemiological studies the Japanese atomic bomb survivors there appears to be a much higher risk of lung cancer in females than males. So, all this is folded into how you estimate what dose corresponds again to that "3% risk of CA factor" depending on their age. Women can have a 40% or 50% lower dose limit.

BB: According to the study there are three major types of skin cancers of interest: melanoma, basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) (minimal mortality rate) The incidence of skin cancer has risen dramatically due to increase in UV exposures from changes in clothing, lifestyle and diagnosis. Risk of skin cancer from space radiation it is stated, "We estimate that the probability of increase skin cancer risk varies more than 10 fold for individual astronauts and that the risk of skin cancer could exceed 1% for future lunar base operations for astronauts with light skin color and hair. Limitations in physical dosimetry in estimating distribution of dose at the skin suggest that new biodosimetry methods be developed for responding to accidental overexposure of skin during future space missions."What about these types of skin cancers and how does race (skin color) enter into CA risk assessment?

FC: Radiation does not appear to cause Melanoma, but it does cause other types of skin cancer like BCC. In the general population BCC occurs more frequently than Melanoma, but is much less fatal. Very few people die from BCC as opposed to Melanoma where you have a high chance of dying. Fortunately radiation does not cause Melanoma. The issue you brought up refer to skin cancer risks and its possible dependence on race, skin color, hair color, and it's known that both background rates are much higher in whites with blue eyes and blond hair.

BB: How would individuals living on the beaches of Florida compare to those living in high altitudes in say... Colorado, would those individuals be more tolerant to space radiation?

FC: For that particular type of cancer (BCC) if you have light skin, light hair it seems like you're more sensitive to skin cancer caused by radiation. It has been suggested that a combined exposure from UV and ionizing radiation enhances the risk.

BB: So person living at high altitude is more tolerant than person living at low altitude?

FC: No, It's not a question of sunlight exposure amount; it's the amount of Melatonin in your skin that's the key factor.

BB: It's an intrinsic factor in the body.

FC: Yes. For example skin cancer rates in Australia there's a much higher rate of sun exposure in Australia than a lot of other places and you have a population frequented by people with light hair and skin. Skin cancer rates in Australia are fairly high. But if you put someone from Italy in Australia their rates would be much lower so the same UV exposure, but the difference in Melatonin appears to be the key factor.

BB: Do you have any advice for students, teachers or young professionals wishing to pursue study and lesson plans in the field of nuclear health science and safety?

FC: I think the basic sciences like molecular biology is where the future improvements in risk assessment and radiation protection will come from. If you look at historically using phenomenological approaches that are not based in basic science they're just too uncertain. You can project risk that way, but the error bars in your projection are just too high. So we're going into a future where knowledge from basic biology, especially molecular biology will be used in our risk assessments. My advice is try and get an education in molecular biology and apply it to the types of problems you brought up.

BB: Do you feel confident the space radiation health and safety community will find a workforce with the necessary skills, training experience to perform NASA's "New Space Vision" requiring space nuclear technology?

FC: We're enhancing student training and I think we'll do well.

BB: Dr. Cucinotta could you explain to our readers how you happened to join into the field of radiation health and safety?

FC: I was interested in nuclear sciences at the University. I attended Old Dominion University it had a lot of programs with NASA, that's how I got my start.

BB: Thank you very much for granting us this interview.

FC: Good luck, Thank you, Bye.

[  PART I   ]